public static void main(String[] args) {
	Scanner scanner=new Scanner(System.in);
	System.out.println("input:");
	int n=scanner.nextInt();
	int a=factorial(n);
	System.out.println(n+"! = "+a);
}
public static int factorial(int n) {
	if (n==1) {
		return 1;
	} else {
		return n*factorial(n-1);
	}
}
